Here's what I do.
Birds go about every 10-20 minutes or so. I have a paper towel
ready and every 10 or 15 minutes I have the bird step up and hold
her over the paper towel and say, "potty". She goes almost every
time. It's a really neat trick to show off to people who are not
"bird people." They think she is trained to go on command. hahahaha
Now she's not potty trained per se and if I forget and let her go
too long she will use my shoulder as a toilet. BTW she is a
peachfaced lovebird named Wilma.